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Research Papers: Gas Turbines: Structures and Dynamics

Computational Fluid Dynamics Investigation of Brush Seal Leakage Performance Depending on Geometric Dimensions and Operating Conditions

[+] Author and Article Information
Yahya Dogu

Department of Mechanical Engineering,
Kirikkale University,
Yahsihan, Kirikkale 71450, Turkey
e-mail: yahya.dogu@hotmail.com

Ahmet S. Bahar

Department of Mechanical Engineering,
Kirikkale University,
Yahsihan, Kirikkale 71450, Turkey
e-mail: ahmetserhatbahar@gmail.com

Mustafa C. Sertçakan

Department of Mechanical Engineering,
Kirikkale University,
Yahsihan, Kirikkale 71450, Turkey
e-mail: mcem_sertcakan@hotmail.com

Altuğ Pişkin

TUSAS Engine Industries, Inc. (TEI),
Eskisehir 26003, Turkey
e-mail: altug.piskin@tei.com.tr

Ercan Arıcan

TUSAS Engine Industries, Inc. (TEI),
Eskisehir 26003, Turkey
e-mail: ercan.arican@tei.com.tr

Mustafa Kocagül

TUSAS Engine Industries, Inc. (TEI),
Eskisehir 26003, Turkey
e-mail: mustafa.kocagul@tei.com.tr

1Corresponding author.

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 15, 2015; final manuscript received August 12, 2015; published online October 6, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 138(3), 032506 (Oct 06, 2015) (13 pages) Paper No: GTP-15-1322; doi: 10.1115/1.4031370 History: Received July 15, 2015; Revised August 12, 2015

Brush seals require custom design and tailoring due to their behavior driven by flow dynamic, which has many interacting design parameters, as well as their location in challenging regions of turbomachinery. Therefore, brush seal technology has not reached a conventional level across the board standard. However, brush seal geometry generally has a somewhat consistent form. Since this consistent form does exist, knowledge of the leakage performance of brush seals depending on specific geometric dimensions and operating conditions is critical and predictable information in the design phase. However, even though there are common facts for some geometric dimensions available to designers, open literature has inadequate quantified information about the effect of brush seal geometric dimensions on leakage. This paper presents a detailed computational fluid dynamics (CFD) investigation quantifying the leakage values for some geometric variables of common brush seal forms functioning in some operating conditions. Analyzed parameters are grouped as follows: axial dimensions, radial dimensions, and operating conditions. The axial dimensions and their ranges are front plate thickness (z1 = 0.040–0.150 in.), distance between front plate and bristle pack (z2 = 0.010–0.050 in.), bristle pack thickness (z3 = 0.020–0.100 in.), and backing plate thickness (z4 = 0.040–0.150 in.). The radial dimensions are backing plate fence height (r1 = 0.020–0.100 in.), front plate fence height (r2 = 0.060–0.400 in.), and bristle free height (r3 = 0.300–0.500 in.). The operating conditions are chosen as clearance (r0 = 0.000–0.020 in.), pressure ratio (Rp = 1.5–3.5), and rotor speed (n = 0–40 krpm). CFD analysis was carried out by employing compressible turbulent flow in 2D axisymmetric coordinate system. The bristle pack was treated as a porous medium for which flow resistance coefficients were calibrated by using literature based test data. Selected dimensional and operational parameters for a common brush seal form were investigated, and their effects on leakage performance were quantified. CFD results show that, in terms of leakage, the dominant geometric dimensions were found to be the bristle pack thickness and the backing plate fence height. It is also clear that physical clearance dominates leakage performance, when compared to the effects of other geometric dimensions. The effects of other parameters on brush seal leakage were also analyzed in a comparative manner.

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Figures

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Fig. 1

Representative brush seal geometry, CFD model domain, and boundary conditions

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Fig. 2

Representative mesh view at fence height region

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Fig. 3

Pressure contours for representative line-to-line (a)–(c) and clearance (0.005 in.) (d)–(f) cases

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Fig. 4

Velocity magnitude contours for representative line-to-line (a)–(c) and clearance (0.005 in.) (d)–(f) cases

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Fig. 5

Velocity vectors for representative line-to-line (a)–(c) and clearance (0.005 in.) (d)–(f) cases

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Fig. 6

Velocity vectors around fence height region for representative line-to-line (a)–(c) and clearance (0.005 in.) (d)–(f) cases

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Fig. 16

Effect of rotor speed on leakage

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Fig. 15

Leakage rate distribution for clearance operation

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Fig. 14

Effect of clearance and pressure ratio on leakage

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Fig. 13

Effect of bristle free height on leakage

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Fig. 12

Effect of backing plate fence height on leakage

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Fig. 11

Effect of bristle pack thickness on leakage

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Fig. 10

Leakage versus pressure ratio for line-to-line and clearance (0.010 in.) cases

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Fig. 9

Radial pressure distribution over backing plate for line-to-line and clearance (0.005, 0.010, and 0.020 in.) cases

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Fig. 8

Radial pressure distribution over backing plate for clearance (0.005 in. and 0.010 in.) cases

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Fig. 7

Radial pressure distribution over backing plate for line-to-line cases

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